1. Field of the Invention
This invention relates to a lawn mower having driving front wheels and driving rear wheels, the mower comprising a mower unit mounted between the front wheels and the rear wheels to be vertically movable, an engine mounted to a front portion of a vehicle body, a transmission case disposed rearwardly of the engine, and an HST coupled to a rear wall of the transmission case.
2. Description of the Related Art
A mid-mount, riding lawn mower having a mower unit mounted between front wheels and rear wheels is known from e.g. Japanese Patent Application “Kokai” No. 2003-106412. In this, an engine and right and left front wheels are arranged on a front portion of the vehicle body and a transmission case having rear wheels on the right and left sides thereof is arranged on a rear portion of the vehicle body. Power from the engine is shaft-transmitted to the HST coupled to a front face of the transmission case 6. Then, speed-changed power available from this HST is divided inside the transmission case into one power portion to be transmitted to the rear wheels and the other power portion which is is shaft-transmitted to the front wheels 2. Further, the mower unit is mounted between the front wheels 2 and the rear wheels 3 to be vertically movable. In the case of such riding lawn mower, a front-wheel driving shaft for transmitting the power from the transmission case to the front portion of the vehicle body is disposed at a high position not to interfere with an upward movement of a mower implement 1. In doing so, since the HST is coupled to the front face of the transmission case, it is necessary to either cause the front-wheel driving shaft to extend through the HST or to arrange the HST at a position laterally retracted away therefrom. However, in the former case, for such insertion of the front-wheel driving shaft through the HST, it is needed to increase the physical size of this HST to allow accommodation of the change speed mechanism therein. In the latter case, for such arrangement of the front-wheel driving shaft laterally away from the HST, it is needed to increase the lateral width of the transmission case.
In an attempt to overcome the above-described problem, a lawn mower is known from U.S. 2003/0106296A1, in which the HST is mounted to a rear wall of the transmission case. Regarding this lawn mower, however, the above cited document lacks any disclosure respecting arrangements of a charge pump and a power transmission shaft for the charge pump required for the HST. In the absence of contemplations respecting such arrangements of charge pump and power transmission shaft, it is not possible to achieve sufficient compactness in the powertrain consisting of the transmission case and the HST employed in the mid-mount riding lawn mower.